that's rather odd, I haven't had a problem with xenia. I bought a two head of redsea pulsating xenia, and a one head of xenia for my girlfriend. Both are doing incredibly well. In my pico though, they are more active, I see they already split from two head to three head, and they must be slowly weeding to other areas of my pico.
In my girlfriends JBJ, nothing special, but I do notice that at the end of her rock, two or three little arms are forming and pulsating too. So in my case no problems here. I think DJconn has had no problems either, he's had them grow like crazy and he's fragged them and had them up for sale or trade.